1. Field of the Invention
This invention relates to an armrest unit for a chair, more particularly to a height-adjustable armrest unit for a chair.
2. Description of the Related Art
U.S. Pat. No. 5,318,347 discloses a height-adjustable armrest unit for a chair. The armrest unit includes a support, a vertical sleeve, and a leverage body. The support is adapted to be mounted securely on a seat of the chair and includes a vertical plate portion with a column of positioning holes formed therethrough. The sleeve is disposed on the vertical plate portion of the support and has a pair of pivot holes respectively formed in inner surfaces of two opposite walls thereof. The leverage body includes an actuated upper portion, an engaging tongue projecting from a lower end portion of the leverage body to engage selectively one of the positioning holes in the support, and a pair of pivot pins respectively secured to an intermediate portion of the leverage body between the actuated upper end portion and the engaging tongue so as to engage the pivot holes in the vertical sleeve respectively. Accordingly, when the actuated end portion of the leverage body is actuated to disengage the engaging tongue of the leverage body from one of the positioning holes in the support, the assembly of the leverage body and the vertical sleeve can be moved relative to the support so as to engage the engaging tongue of the leverage body within another one of the positioning holes in the support, thereby adjusting the height of the sleeve.
A drawback of the above-mentioned adjustable armrest unit resides in that during the height adjustment operation, the assembly of the vertical sleeve and the leverage body may occasionally and accidentally disengage from the plate portion of the support, thereby inconveniencing the user of the chair.